1. Field of the Invention
The present invention relates to a pressure measuring method and device that measure the pressure in a pipe, which are used for diagnosing the condition of the pipe feeding gas or liquid. In particular, it relates to the pressure measuring method and device that detect leakage of a gas or a liquid from the pipe.
2. Related Art Statement
Many pipes are installed in buildings of home and factory, and these are utilized for supplying various gases or various liquids, such as town gas, liquefied petroleum gas, potable water, refrigerant for air conditioning, gas and solution for plant, to every place in a building.
However, by mechanical or chemical action, these pipes may be deteriorated gradually when being used over a long period of time, and possibly there may occur a problem that an opening is generated in a wall of the pipe and a gas or a liquid carried inside the pipe is leaked.
Therefore, periodical leakage inspections of many of these pipes are made compulsory by decree, etc. For example, when consumer uses liquefied petroleum gas (LP gas), an inspection of facilities, such as a pipe, is made compulsory by “Law Concerning the Securing of Safety and the Adequacy of Transaction for Liquefied Petroleum Gas (common name: Liquefied Petroleum Gas Law)”.
So far, the leakage inspection of a pipe has been conducted by holding the pipe in the closed state, injecting a gas or a liquid from an inlet, such as a feed opening or an exhaust, that is installed in a part of the pipe and is communicated with the inside of the pipe, making the inside of the pipe higher pressure condition than the outside of the pipe, and then, measuring the pressure change in the pipe beyond the predetermined time.
Then, in the result of the measurement, for example, if it is shown that pressure is on a downward trend, it is assumed that the gas or the liquid is flowing out of the inside of the pipe, and it is judged accordingly that there is an opening, such as crack in a part of the wall of the pipe.
In addition, it takes a different amount of time for an inspection depending on the volume of the pipe that is being inspected. There is a tendency, generally, that the bigger the volume of the pipe is, the longer it takes for inspection.
Moreover, in order to measure the amount of leakage of a gas or a liquid, since it is notpossible to calculate only by measuring the pressure change in a pipe, it is necessary to calculate the volume of the pipe in the closed state separately.
However, on the grounds that the volume of the pipe that is an object of inspection cannot be easily measured for real, in case of inspecting a domestic gas piping etc., inspection providers set the measuring time amount by estimating the volume of the pipe experientially or intuitively, and utilize the volume of a pipe calculated based on an engineering-drawing of a pipe work etc. for the measurement of leakage amount. Therefore it makes it difficult to improve the accuracy of the inspection sufficiently.
Furthermore, the pressure change in the pipe held in the closed state is not caused only by leakage, but the pressure changes due to a change in temperature etc. in the pipe.
Therefore, the measurement in consideration of the influences of this temperature change is required for an accurate inspection, however, as there exists no easy-to-use measurement device up to now that can measure the temperature change in a pipe simultaneously with the measurement of the pressure change of the pipe, the measurement has been conducted by selecting the time when a temperature change is small, and it has been the cause of the operation efficiency of the inspection falling remarkably.
The present invention intends to solve the above-mentioned objects and to provide the pressure measuring method and device that are capable of easily measuring the volume of a pipe that is an object of inspection and of eliminating the influences of a change in temperature in the pipe.
Further, as to the pressure measuring device of the present invention, it intends to provide the functions and the structure for preventing the operation of the pressure measuring device from cumbersomeness and the said device from complication, even when adding new functions, such as the measurement of the pipe volume or the elimination of the influences of a change in temperature.
Also, by displaying the past measurement results of each client and enabling the comparison of the present measurement value with the past measurement results, it intends to provide a diverse and novel inspection method of a pipe, with which the longitudinal change can be observed, or on which is based in evaluating the abnormality of the present measurement value, etc.